Process of preparing ferrous chloride from mixed chlorides of iron and nickel



Patented May 4, 1954 FR OCESS OF PREPARING FERROUS CHLO- RIDE FROM MIXED CHLORIDES OF IRON AND NICKEL Marion Ernest Graham, Parma, and Edward A. Beidler, Columbus, Ohio, assignors, by mesne assignments, to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey No Drawing. Application May 8, 1950, Serial No. 160,821

4.- Claims. 1

Our present invention relatesto a process for preparing substantially pure ferrous chloride from mixed iron chloride and nickel. A particular embodiment of the invention is as a particular step in a larger overall process of treating mixtures of iron with nickel and possibly other metals, which mixtures are obtained by treating ores or alloys containing these metals or some of them and possibly other metals in the cas of alloys and natural ores, and also gan ue in the case of ores. In the overall process above generally referred to, the first step of the process, which forms no necessary part of the present invention, is to chloridize the original material. This converts a substantial amount of the iron present in the original material to ferrous chloride. Some of the iron may, however, be originally present in the form of metallic iron or may be converted to metallic iron. This is particularly true in the event that the chloridizing is accompanied by a reducing action provided in any appropriate way. Nickel, if present, will be converted at least in part to the form of nickel chloride, NlClz, while some of these metals may be present in, or be converted to the metallic form in the same way as the iron. Other metals may, for example, be present in the original material being treated, for example, chromium when the material is stainless steel scrap or certain types of ores.

Gang'ue may also be present, in the event that the original material is a natural ore, this gangue being alumina, silica, possibly also magnesia, or more or less complex compounds of these materials commonly found in natural ores.

The present invention may be considered as being applicable following the chloridizing of the original material Whatever it may be and whatever its source may be. As such, the essential active ingredients of the material forming the input to the process of the present invention are (a) ferrous chloride (FeClz) and (b) nickel chloride (NiClz).

The general purpose of the present invention is to enable the ferrous chloride to be separated from the remaining materials as substantially pure ferrous chloride free of the chlorides of nickel. At the same time it is an object of the invention to convert any nickel chloride initially present to the form of elemental nickel. It is recognized that the elemental nickel thus formed may not remain as such, but may possibly combine with the metallic iron originally present as aforesaid to form some nickel-iron alloy. However, the broad purpose is secured, which i to retain the nickel in a non volatile 2 form, while separating the F8012 therefrom by vaporization.

In the prior art illustrated, for example in the patents to Kroll, Nos. 2,396,792-3- l, all issued March 19, 1945, an attem t was made to separate ferrous metallic impurities from nickel. In accordance with these Kroll patents, it was attempted to carry out a transfer reaction between iron in elemental form and nickel chloride, so as to form nickel in elemental form and ferrous chloride. This was accomplished by Kroll in accordance with one of the patents aforesaid in a fused salt bath. In another of the Kroll patents aforesaid the same reaction was attempted to be accomplished without the bath, but conditions otherwise bein substantially the same. In the third of these patents the purpose was to chloridize nickel and iron in a fused bath b passing chlorine therethrough; and the reaction aforesaid was relied upon to get selective chloridizing of the iron without chloridizing the nickel. In all the Kroll disclosures, the purpose was basically to provide pure nickel and to free this nickel from iron, among other metals, as an impurity, the iron being present in a very small amount in respect to the amount of nickel present. There was no attempt in accordance with the Kroll disclosures to effect a physical separation simultaneously with the principal chemical transfer reaction as aforesaid, but the physical separation was to be efiected subsequent to the chemica1 reaction and by solution in a fused salt bath or by leaching in an aqueous solution, for example. In one of these patents, Kroll disclosed specifically that the chemical transfer reaction aforesaid is a reversible type reaction, which proceeds only to some intermediate equilibrium stage. In order to bias the equilibrium in a desired direction, Kroll resorted to the expedient of adding a substantially large excess of nickel chloride, 25% to 50%, for example.

The present application is one of a group of seven co-pending applications, all the inventions of the same inventors, four of these cases relating to nickel and reactions involvin nickel and the other three relating to cobalt and reactions involving cobalt. The cases may be compared and distinguished as follows:

a. Ser. No. 160,821, filed May 8, 1950 (the present application), relates to treating a starting material in the non-gaseous (liquid and/or solid) form and consisting essentially of NiClz and FeClz, and wherein there is more FeClz than NiClz. This starting material is treated in a reaction or 155 sublimation zone, in the presence of a certain amount of metallic iron, to produce a final product which is vaporized FeClz, removed from the sublimation zone as such, leaving only metallic iron and metallic nickel in the sublimation zone.

b. Ser. No. 210,433, filed February 10, 1951, relates to treating a starting material, essentially the same as Ser. No. 160,821, except that in this instance the startin material is introduced into the reaction zone in a solely gaseous state. The reaction and the final products are substantially the same as in Ser. No. 160,821.

0. Ser. No. 160,822, filed May 8, 1950, relates to the preventing or minimizing of a possible back reaction. The starting material consists essentially of ferrous chloride and metallic nickel. It is desired to separate these materials without permitting, or at least minimizing, a possible back reaction therebetween which would produce nickel chloride and metallic iron. To do this, the startin material is introduced into a reaction or sublimation zone in which metallic iron is present. The starting material as introduced into this zone is in a non-gaseous state. The final products are substantially pure ferrous chloride vapor, which is removed from the zone as such, and metallic nickel and metallic iron which remain in the zone.

(2. Ser. No. 294,058, filed June 17, 1952, discloses a process for treating a starting material substantially the same as in Ser. No. 160,821. This case has been amended so as to preclude the claims reading upon separation of the products of the reaction by vaporization as in Ser. No. 160,821; but in this case the separation followin the reaction is efiected by Withdrawin the metallic nickel produced (by a reaction the same as in Ser. No. 160,821) by withdrawing massive pieces of iron, to which the deposited nickel adheres physically, from the fused bath of the starting materials. Neither the ferrous chloride nor any nickel chloride present is intentionally volatilized. This application is junior to application Ser. No. 160,821, so that the only subject matter claimable therein is subject matter which cannot be supported by the disclosure of Ser. No. 160,821; all the common subject matter being claimed in Ser. No. 160,821.

e. Ser. No. 291,816, filed June 4, 1952, is the first of the three cobalt applications and is the cobalt counterpart of the nickel case, Ser. No. 160,821, distinguishing therefrom by being directed to cobalt and its chloride, rather than nickel and its respective chloride. This case is further distinguished in the degree of purity of the sublimate.

1. Ser. No. 320,835, filed November 15, 1952, is the cobalt counterpart of nickel case, Ser. No. 210,433. It distinguishes from cobalt case Ser. No. 291,816 in the same way discussed above as to the respectively corresponding nickel cases, while distinguishing from its corresponding nickel case, Ser. No. 210,433, by the differences between cobalt and nickel.

g. Ser. No. 321,514, filed November 19, 1952, is the cobalt case corresponding to the nickel case Ser. No. 160,822. It distinguishes from the other cobalt cases as discussed above in respect to the respective corresponding nickel cases, while distinguishing from its nickel counterpart, Ser. No. 160,322, by the differences between nickel and cobalt.

In accordance with the present invention, the basic material to be Worked upon in accordance with the present process is contemplated to contain relatively large percentages of iron, principally in the form of ferrous chloride, as compared with the amount or nickel. For example, in one ore which has been treated in accordance with the present process there is contained about thirty times as much iron as nickel. Even in treating stainless steel scrap, for example, the percentage of iron is far greater than the percentage of nickel present. This difference in raw material, however, is not presently relied upon as a basic distinction from the prior art, but is mentioned as illustrating a diiference in the type of material which the present invention is adapted to treat, as compared with the material contemplated for use in the prior art.

In accordance with the present invention, it i contemplated that there Will be present during the reaction sufficient iron in elemental form to react with all the chlorine initially introduced in the form of nickel chloride. so as to form therefrom ferrous chloride by the chemical transfer reaction aforesaid. Preferably also there will be a reasonable excess of elemental iron initially present over such equivalent or stoichiometric proportions as hereinafter more particularly set forth. The transfer reaction is basically the same as that which was contemplated in accordance with the prior art teaching as described. However, in the present case the reaction is caused to carry through to substantial completion, irrespective of the reversible character of the reaction and some intermediate equilibrium end point, by separating from the process the ferrous chloride substantially as it is formed. Specifically, the present invention contemplates the distillation separation of ferrous chloride, including both the ferrous chloride which is initially present in the material supplied to the process and that which is formed by the chemical transfer reaction aforesaid. For this purpose the temperature will be adjusted to a point such that the ferrous chloride present will have an appreciable vapor pressure, and if necessary, a sweep gas will be used to convey the ferrous chloride vapor away from the remaining substantially solid materials,

Considering now the details of the present process, it is wholly immaterial what the sources of the solid materials are going into the process. Any preliminary steps eifected on such raw materials form no part of the present invention. The material entering the process in all instances contains ferrous chloride, FeClz. It further contains nickel chloride (NiClz). This material may or may not contain one or both of the metals, iron and nickel, in elemental form. It may also contain more or less, or even none, of other metallic oxides or chlorides, or such inert earthy materials generally classed as gangue in the metallurgical field.

In accordance with the present invention it is determined whether or not there is sufiicient elemental iron present to carry on the desired reaction in accordance with the present invention. This reaction may be generally expressed by the equation:

In practice it is desired that there be a certain excess of elemental iron over the exact equivalent proportions as aforesaid. The amount of this excess need not be great, nor is it critical. It is dependent in practice upon the particle size of the material and of the iron present, the degree and thoroughness of the mixing and upon any limitations imposed by the desired or intended use of the remaining raw materials. It is usually desired that the excess of iron be substantial, for example two to three times the minimum amount necessary to react with all the chlorine introduced into the process as NiClz. The reason for this is that it is desired to be certain. that there is always enough iron present at points in proximity with any nickel chloride present, so that the reaction as given above can occur in the desired direction and to completion. If the iron is present in extremely small particle size, the requirements for excess iron are less rigid and are less in amount than if the iron were present in relatively larger particle size. If the mixing is more thorough, the excess of iron need not be so great. Theoretically if the materials were of infinitely small particle size and the mixing theoreticaly perfect and homogeneous throughout, no excess of iron would be required. Thus the actual excess which should be used in accordance with the present invention is to compensate for the practical probability that there could be a few atoms of chlorine bonded to nickel at one portion of a mix and enough iron to react with it at some other portion thereof, but the two might never get together hysically or chemically. When an adequate excess of metallic iron is provided, this condition cannot obtain. Actual examples will appear hereinafter showing amounts of iron found in practice to be desirable in use.

In some starting mixtures of materials which may be supplied to this process, there will be an adequate amount of metallic iron present to comply with the requirements of the process as hereinabove set forth. In such an event it will be unnecessary to add metallic iron. In other materials supplied to the process, it will be practically necessary to add some iron. In such an event only, the addition of iron is an essential step of the present process. The term providing metallic iron or equivalent language as used in the appended claims includes either a starting material which has an adequate amount of metallic iron present initially or a starting material which did not initially contain sufficient or any metallic iron, but to which metallic iron has been added.

The present process is effected primarily as a single step, during which the material is maintained at a desired temperature or within a selected, desired temperature range. In the event that the material comes from a prior process, at the termination of which it is already'heated,

it may be sufficient to maintain it at the temr perature which it has on entering the present process. However, in the usual case it will be necessary to heat up the material. The temperature range in the present case is that in which the vapor pressure of ferrous chloride is sufliciently great, so that it may volatilize at a desired rate. As will be understood, the vapor pressure of ferrous chloride increases progressively with increasing temperature. Thus there is not definite or critical low limit of temperature for the present process. It is noted, for example, that the melting point of ferrous chloride is about 728 C. In some instances it may be desired to operate at a temperature even less than the melting point, for example about as low as about 600 C. Below about this temperature, the vapor pressure of ferrous chloride is so low that the rate of volatiliza-tion thereof is below an economically practicable value. At the same time, the actual temperatureto be chosen above the predetermined low limit will depend primarily upon economics and upon factors other than temperature itself.

The high temperature limit is believed to be about that of the boiling point of ferrous chloride, which at atmospheric pressure is about 1025 C. In view of the fact that the volatilize.- tion of ferrous chloride is an endothermic process, the temperature of the solid (and/or liquid) mass cannot exceed this boiling point as long as any substantial amount of ferrous chloride remains nonvolatilized. The vaporization of ferrous chloride, which absorbs heat, will keep the temperature from exceeding about this boiling point as long as there is ferrous chloride present, in either solid or liquid form. The high limit of temperature, therefore, is selected as the boiling point of ferrous chloride. It will be understood, however, that in some installations it may be possible to maintain the materials under superatmospheric pressure, in which event a somewhat higher absolute temperature limit would be permissible for use, in that the boiling point of ferrous'chloride is a function of pressure.

Further as to the melting point of the materials present in a solid material supplied to the process, it has been found that the melting point diagram of a mixture of ferrous chloride mixed with nickel chloride indicates generally higher temperatures for melting points of mixtures than for pure ferrous chloride. Thus it may be desired and is to be included in the purview of the present invention that the process be carried on at temperatures lower than the actual melting temperatures of the iron and nickel chlorides present.

In general, it may be said that while the temperature is not particularly critical, the rate of removal of ferrous chloride from the material present is, of course, a function of temperature, so that the process is completely operative throughout a large temperature range as stated, the rate differing with different temperatures. The exchange reaction by which ferrous chloride is formed and nickel chloride reduced to elemental nickel occurs at least as rapidly as the resulting ferrous chloride can be removed from the process by vaporization. The temperature and time period for the process is therefore a joint function, each of the other, and both of the amount of ferrous chloride present initially plus the amount of ferrous chloride which is formed in accordance with the process.

In the event that the temperature of the reaction as aforesaid is to be maintained substantially at the boiling point of ferrous chloride, then this material would have a sufficient vapor pressure so that it could pass from the solid and/or liquid material without assistance, and per se flow out of the system and to a point to which it is desired to pass the ferrous chloride vapor. If on the other hand, some lower temperature is employed, which is within the scope of the present invention as aforesaid, then some sweep gas should be used in order that the ferrous chloride vapor be separated from the solid and/or liquid material remainder and be passed to a desired point. It is usually contemplated in accordance with the present invention that any sweep gases employed will be essentially neutral or inert in character in respect to the various ofthe, gases present is not sufficient to change age-mecca the reaction taking place in anon-desired:

manner.

In the normal operation, in accordance with the present process, ferrous chloride vapor will be conveyed out of the apparatus in which. the

reaction proper is carried on and to some other apparatus. It is contemplated that the present process may be carried on either as. an intermittent or batch process on the one. hand, or as a continuous or semi-continuous process on the other, and in any desired type of apparatus which will be appropriate. The present invention is not restricted to any one type of apparatus, but many will suggest themselves to those skilled in the art from the present description of the process itself.

It is contemplated that under certain circumstances ferrous chloride vapor may be desirable for certain subsequent processes as such. If so, then this vapor may be passed directly to such further process. On the other hand, it may be desired to condense this vapor to a liquid and/or solid condition. If so, such condensation may be carried on in any appropriate condensin apparatus, from which the heat of vaporization may be recovered by any suitable heat recovering system if desired. The subsequent use of ferrous chloride vapor forms no necessary part of the present invention and hence will not be further described herein.

The solid materials remaining at the termination of the operation of the separation of all the ferrous chloride therefrom in accordance with the present invention may be further processed for the recovery of one or more of the valuable ingredients thereof. For example nickel may be recovered from this solid material by anysuitable process, for example by mechanical: or magnetic separation or by some chemical treatment involving one or more steps, all of which per se form no part of the present invention. Such processes for the recovery of metal values may include those well known in the art and will not be further discussed herein.

The process of the present invention is further illustrated in the following examples:

Example I The process was operated using a mixture of 88% FeClz, 3% M012 and 9% Fe, in a tempera-- r ture range from just below 600 C. up to about.

650 C. Notwithstanding the large preponderance of ferrous chloride present, less than .05% of the sublimate was nickel chloride, the remainder being ferrous chloride.

Example II With an initial material containing nickel chloride 2.7%, ferrous chloride 87.3%, and iron 10.0%, at a temperature of about l,000 C. over 99% of the ferrous chloride was found'in the sublimate, which contained zero nickel chloride.

The importance of the presence of metallic iron is illustrated by the following example, not in accordance with the present invention.

Example III hand, it is noted that there was little or no nickel chloride in the sublimate, which is an unexpected result based upon the fact that nickel chloride has a sublimation temperature quite close to that of ferrous chloride (about 975 C. for nickel chloride as compared with about 1025 C. for ferrous chloride). The vapor pressure curves of the two materials are quite close together throughout a large range of temperature including the range contemplated for use in accordance with the present. invention.

A further illustration indicating the necessity for some excess of iron to be present and for the ne ss y of? having the iron in a finely divided condition and; in: intimate mixture with the remaining material is where a still bed of equi-molar quantitiesv of FeCh, NiClz and Fe was exposed at a temperature in the range of about 600 up to about 760 C. for a time period of one to two hours. As against an initial 41% (by weight) nickel chloride in the starting material, 8.3% of the nickel chloride found its way into the sublimate. In this experiment substantially all the ferrous chloride passed into the sublimate. From this and other work, the requirement for a reasonable excess of iron has been deduced.

The fact that the reaction (nickel chloride plus iron gives iron chloride plus nickel) is a reversible reaction having an equilibrium intermediate the terminal conditions in each direction is further illustratedby an example wherein a mixture containing 91% ferrous chloride and the balance metallic nickel was exposed to the same temperature conditions as in several of the above examples. Under these conditions about 7% of the metallic nickel initially present was found in the sublimate as nickel chloride, indicating the back reaction or reversible character of the above reaction tending toward an intermediate equilibrium condition. This occurred when no metallic iron was present and is to be compared with conditions wherein, even though nickel chloride was originally present and tends to volatilize at least as much if not more than the ferrous chloride, substantially no nickel chloride is found in the sublimate, due to the reaction equilibrium being driven in the desired direction by abstracting from the system one of the products thereof, namely by separated vaporized ferrous chloride as it is formed from the system wherein the equilibrium tends to be established.

While we have described our process in general and have set forth in some detail the chemical and physical requirements thereof, it is recognizedthat the process may be varied by the substitution of equivalents as will suggest themselves to those skilled in the art from the foregoing disclosure. We do not wish to be limited, therefore, except by the scope of the appended claims, which are to beconstrued validly, as broadly as the state of the prior art permits.

What is claimed is:

1. The process of separating ferrous chloride, substantially free of NlClz, from a starting mat rial containing both NlClz and E9012, and in which there is a greater amount of FeClz and NlCl2, which comprises introducing said material into a reaction-zone in a non-gaseous state, providing sufficient metallic iron in sald zone and in contact with the non-gaseous material the -ein to assure that there is present at least suffi 'ent metallic iron to react with all the chlorine which is present in said zone in the form of Nick to form FeClz, maintaining the material in said zone within the temperature range of about 600 C. up to the boiling point of FeClz at the pressure existing in said zone for a time and under conditions such that the actual gaseous pressure exerted by FeClz vapor in said zone is less than the equilibrium vapor pressure of pure FeClz at the temperature existing in said zone, so that the FeClz introduced as such into said zone and the FeClz which is formed in said zone by a reaction between the metallic iron present and NiC12 is substantially vaporized and until substantially all the NiClz has been converted by said reaction to a non-volatile form of nickel, and separating the volatilized FeClz, substantially free of NiClz.

2. The process according to claim 1, wherein the temperature at which said material is maintained is about but not over the boiling point temperature of ferrous chloride at the pressure to which said material is exposed.

3. The process according to claim 1, comprising the additional step of passing over said material a sweep gas, which is inert in respect to all the materials present, so as to assist in the removal from said material of the vapors of FeClz, and thereby separating vaporized FeClz from the remainder of said material.

4. The process according to claim 1, wherein the amount of metallic iron provided in said zone in contact with the non-gaseous material therein is at least twice that amount which is stoichiometrically equivalent to the amount of chlorine introduced into said zone in the form of NiClz in said starting material, said metallic iron being in a finely divided form; wherein the material in said zone is maintained at a temperature of about 1025 C.; and wherein the total gaseous pressure in said zone is maintained at about atmospheric pressure.

Name Date 2,067,874 Brown et al Jan. 12, 1937 2,396,792 Kroll Mar. 19, 1946 OTHER REFERENCES J. W. Mellors "A Comprehensive Treatise on Theoretical and Inorganic Chemistry, vol. 15,

page 418; vol. 14, page 11; Longmans, Green and Co., New York, N. Y. 

1. THE PROCESS OF SEPARATING FERROUS CHLORIDE, SUBSTANTIALLY FREE OF NICL2, FROM A STARTING MATERIAL CONTAINING BOTH NICL2 AND FECL2, AND IN WHICH THERE IS A GREATER AMOUNT OF FECL2 AND NICL2, WHICH COMPRISES INTRODUCING SAID MATERIAL INTO A REACTION ZONE IN A NON-GASEOUS STATE, PROVIDING SUFFICIENT METALLIC IRON IN SAID ZONE AND IN CONTACT WITH THE NON-GASEOUS MATERIAL THEREIN TO ASSURE THAT THERE IS PRESENT AT LEAST SUFFICIENT METALLIC IRON TO REACT WITH ALL THE CHLORINE WHICH IS PRESENT IN SAID ZONE IN THE FORM OF NICL2 TO FORM FECL2, MAINTAINING THE MATERIAL IN SAID ZONE WITHIN THE TEMPERATURE RANGE OF ABOUT 600* C. UP TO THE BOILING POINT OF FECL2 AT THE PRESSURE EXISTING IN SAID ZONE FOR A TIME AND UNDER CONDITIONS SUCH THAT THE ACTUAL GASEOUS PRESSURE EXERTED BY FECL2 VAPOR IN SAID ZONE IS LESS THAN THE EQUILIBRIUM VAPOR PRESSURE OF PURE FECL2 AT THE TEMPERATURE EXISTING IN SAID ZONE, SO THAT THE FECL2 INTRODUCED AS SUCH INTO SAID ZONE AND THE FECL2 WHICH IS FORMED IN SAID ZONE BY A REACTION BETWEEN THE METALLIC IRON PRESENT AND NICL2 IS SUBSTANTIALLY VAPORIZED AND UNTIL SUBSTANTIALLY ALL THE NICL2 HAS BEEN CONVERTED BY SAID REACTION TO A NON-VOLATILE FORM OF NICKEL, AND SEPARATING THE VOLATILIZED FECL2, SUBSTANTIALLY FREE OF NICL2. 